1. Field of the Invention
The present invention provides a method for producing a catalyst for homo-polymerization or co-polymerization of ethylene, or more particularly a method for producing a high-activity titanium solid complex catalyst supported on a carrier containing magnesium, wherein said catalyst is capable of producing polymers with high bulk densities and narrow particle size distributions with a low content of fine particles.
2. Description of Related Art
Catalysts containing magnesium for polymerization or co-polymerization of ethylene are known to have very high catalytic activities and to produce polymers with a high bulk density. These catalysts are suitable for liquid phase or gas phase polymerization. Liquid phase polymerization of ethylene denotes a polymerization process performed in a medium such as bulk ethylene, isopentane, or hexane. One of the important characteristics of catalysts used in this process is catalytic activity. The characteristics of the catalyst will also affect bulk density of the resultant polymers, content of low molecular weight molecules of the resultant polymers dissolved in a medium, particle size distribution of the resultant polymers, and content of fine particles in the resultant polymers.
Many titanium-based catalysts containing magnesium for olefin polymerization, and the manufacturing methods thereof have been reported. Many processes using magnesium solutions to produce catalysts that can generate olefin polymers with a high bulk density are known. A magnesium solution may be obtained by reacting magnesium compounds with electron donors such as alcohols, amines, cyclic ethers, or organic carboxylic acids in the presence of a hydrocarbon solvent. Examples using an alcohol are disclosed in U.S. Pat. Nos. 3,642,746; 4,336,360; 4,330,649; and 5,106,807. Further, methods for production of catalysts containing magnesium by reacting the said liquid-phase magnesium solution with a halogenated compound such as titanium tetrachloride are well known. Such catalysts produce high bulk density polymers, but there are still improvements yet to be made with respect to catalytic activity and hydrogen reactivity. Moreover, tetrahydrofuran, a cyclic ester, has been used as a solvent for a magnesium compound in U.S. Pat. Nos. 4,477,639 and 4,518,706.
U.S. Pat. Nos. 4,847,227; 4,816,433; 4,829,037; 4,970,186; and 5,130,284 teach the use of electron donors such as dialkylphthalate, phthaloyl chloride, etc. for reaction with a titanium chloride compound in the production of olefin polymerization catalysts exhibiting superior polymerization activity, and which are capable of enhancing the bulk density of the resultant polymers.
U.S. Pat. No. 5,459,116 teaches a method of product of a titanium solid catalyst by contact-reacting a magnesium solution containing an ester having at least one hydroxyl group as an electron donor with a titanium compound. By this method, a catalyst of high polymerization activity was obtained, which produces polymers with a high bulk density but there is still room for more improvement.
There is a need for the development of new catalysts for homo-polymerization or co-polymerization of ethylene for producing polymers. The catalyst should have the following characteristics: be produced by a simple manufacturing process, exhibit a high polymerization activity, produce high bulk density polymers by means of controlling catalyst particle size, and in particular, produce a polymer with a narrow particle size distribution containing few fine particles. It is intended to provide a method of producing, from low-cost compounds via a simple process, a catalyst having excellent catalytic activity capable of producing polymers with high bulk densities and narrow particle size distributions containing few fine particles.